In this two-part Channel 4 series, Professor Richard Dawkins challenges what he describes as 'a process of non-thinking called faith'. He describes his astonishment that, at the start of the 21st century, religious faith is gaining ground in the face of rational, scientific truth. Science, based on scepticism, investigation and evidence, must continuously test its own concepts and claims. Faith, by definition, defies evidence: it is untested and unshakeable, and is therefore in direct contradiction with science. In addition, though religions preach morality, peace and hope, in fact, says Dawkins, they bring intolerance, violence and destruction. The growth of extreme fundamentalism in so many religions across the world not only endangers humanity but, he argues, is in conflict with the trend over thousands of years of history for humanity to progress to become more enlightened and more tolerant.